Call tzset() for all compilers before using time zone variable.

Changes of r66245 shouldn't have been specific to MSVC, we must call tzset()
when using any other compiler as well, otherwise time zone information can be
initially incorrect.

Closes #13862.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70332 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/time.cpp

@@ -223,15 +223,22 @@ int wxGetTimeZone()
     #else // VC++ < 8
         return timezone;
     #endif
-#elif defined(WX_TIMEZONE) // If WX_TIMEZONE was defined by configure, use it.
-    return WX_TIMEZONE;
-#elif defined(__BORLANDC__) || defined(__MINGW32__) || defined(__VISAGECPP__)
-    return _timezone;
-#elif defined(__MWERKS__)
-    return 28800;
-#else // unknown platform -- assume it has timezone
-    return timezone;
-#endif // WX_GMTOFF_IN_TM/!WX_GMTOFF_IN_TM
+#else // Use some kind of time zone variable.
+    // In any case we must initialize the time zone before using it.
+    tzset();
+
+    #if defined(WX_TIMEZONE) // If WX_TIMEZONE was defined by configure, use it.
+        return WX_TIMEZONE;
+    #elif defined(__BORLANDC__) || defined(__MINGW32__) || defined(__VISAGECPP__)
+        return _timezone;
+    #elif defined(__MWERKS__)
+        // This is just plain wrong but apparently MetroWerks runtime didn't have
+        // any way to get the time zone.
+        return 28800;
+    #else // unknown platform -- assume it has timezone
+        return timezone;
+    #endif // different time zone variables
+#endif // different ways to determine time zone
 }
 
 // Get local time as seconds since 00:00:00, Jan 1st 1970